Generator.cpp

#include <atomic>
#include <cmath>
#include <condition_variable>
#include <fstream>
#include <memory>
#include <unordered_map>
#include <utility>

#include "CompilerLogger.h"
#include "Generator.h"
#include "IRPrinter.h"
#include "Module.h"
#include "Serialization.h"
#include "Simplify.h"

#ifdef HALIDE_ALLOW_GENERATOR_BUILD_METHOD
#pragma message "Support for Generator build() methods has been removed in Halide version 15."
#endif

namespace Halide {

GeneratorContext::GeneratorContext(const Target &target)
    : target_(target),
      autoscheduler_params_() {
}

GeneratorContext::GeneratorContext(const Target &target,
                                   const AutoschedulerParams &autoscheduler_params)
    : target_(target),
      autoscheduler_params_(autoscheduler_params) {
}

GeneratorContext GeneratorContext::with_target(const Target &t) const {
    return GeneratorContext(t, autoscheduler_params_);
}

namespace Internal {

namespace {

// Return true iff the name is valid for Generators or Params.
// (NOTE: gcc didn't add proper std::regex support until v4.9;
// we don't yet require this, hence the hand-rolled replacement.)

bool is_alpha(char c) {
    return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
}

// Note that this includes '_'
bool is_alnum(char c) {
    return is_alpha(c) || (c == '_') || (c >= '0' && c <= '9');
}

// Basically, a valid C identifier, except:
//
// -- initial _ is forbidden (rather than merely "reserved")
// -- two underscores in a row is also forbidden
bool is_valid_name(const std::string &n) {
    if (n.empty()) {
        return false;
    }
    if (!is_alpha(n[0])) {
        return false;
    }
    for (size_t i = 1; i < n.size(); ++i) {
        if (!is_alnum(n[i])) {
            return false;
        }
        if (n[i] == '_' && n[i - 1] == '_') {
            return false;
        }
    }
    // prohibit this specific string so that we can use it for
    // passing GeneratorParams in Python.
    if (n == "generator_params") {
        return false;
    }
    return true;
}

std::map<OutputFileType, std::string> compute_output_files(const Target &target,
                                                           const std::string &base_path,
                                                           const std::set<OutputFileType> &outputs) {
    std::map<OutputFileType, const OutputInfo> output_info = get_output_info(target);

    std::map<OutputFileType, std::string> output_files;
    for (auto o : outputs) {
        output_files[o] = base_path + output_info.at(o).extension;
    }
    return output_files;
}

Func make_param_func(const Parameter &p, const std::string &name) {
    internal_assert(p.is_buffer());
    Func f(p.type(), p.dimensions(), name + "_im");
    auto b = p.buffer();
    if (b.defined()) {
        // If the Parameter has an explicit BufferPtr set, bind directly to it
        f(_) = b(_);
    } else {
        std::vector<Var> args;
        std::vector<Expr> args_expr;
        for (int i = 0; i < p.dimensions(); ++i) {
            Var v = Var::implicit(i);
            args.push_back(v);
            args_expr.push_back(v);
        }
        f(args) = Internal::Call::make(p, args_expr);
    }
    return f;
}

}  // namespace

std::vector<Type> parse_halide_type_list(const std::string &types) {
    const auto &e = get_halide_type_enum_map();
    std::vector<Type> result;
    for (const auto &t : split_string(types, ",")) {
        auto it = e.find(t);
        user_assert(it != e.end()) << "Type not found: " << t;
        result.push_back(it->second);
    }
    return result;
}

class StubEmitter {
public:
    StubEmitter(std::ostream &dest,
                const std::string &generator_registered_name,
                const std::string &generator_stub_name,
                const std::vector<Internal::GeneratorParamBase *> &generator_params,
                const std::vector<Internal::GeneratorInputBase *> &inputs,
                const std::vector<Internal::GeneratorOutputBase *> &outputs)
        : stream(dest),
          generator_registered_name(generator_registered_name),
          generator_stub_name(generator_stub_name),
          generator_params(select_generator_params(generator_params)),
          inputs(inputs),
          outputs(outputs) {
        namespaces = split_string(generator_stub_name, "::");
        internal_assert(!namespaces.empty());
        if (namespaces[0].empty()) {
            // We have a name like ::foo::bar::baz; omit the first empty ns.
            namespaces.erase(namespaces.begin());
            internal_assert(namespaces.size() >= 2);
        }
        class_name = namespaces.back();
        namespaces.pop_back();
    }

    void emit();

private:
    std::ostream &stream;
    const std::string generator_registered_name;
    const std::string generator_stub_name;
    std::string class_name;
    std::vector<std::string> namespaces;
    const std::vector<Internal::GeneratorParamBase *> generator_params;
    const std::vector<Internal::GeneratorInputBase *> inputs;
    const std::vector<Internal::GeneratorOutputBase *> outputs;
    int indent_level{0};

    std::vector<Internal::GeneratorParamBase *> select_generator_params(const std::vector<Internal::GeneratorParamBase *> &in) {
        std::vector<Internal::GeneratorParamBase *> out;
        for (auto *p : in) {
            // These are always propagated specially.
            if (p->name() == "target" ||
                p->name() == "autoscheduler") {
                continue;
            }
            if (p->is_synthetic_param()) {
                continue;
            }
            out.push_back(p);
        }
        return out;
    }

    /** Emit spaces according to the current indentation level */
    Indentation get_indent() const {
        return Indentation{indent_level};
    }

    void emit_inputs_struct();
    void emit_generator_params_struct();
};

void StubEmitter::emit_generator_params_struct() {
    const auto &v = generator_params;
    std::string name = "GeneratorParams";
    stream << get_indent() << "struct " << name << " final {\n";
    indent_level++;
    if (!v.empty()) {
        for (auto *p : v) {
            stream << get_indent() << p->get_c_type() << " " << p->name() << "{ " << p->get_default_value() << " };\n";
        }
        stream << "\n";
    }

    stream << get_indent() << name << "() {}\n";
    stream << "\n";

    if (!v.empty()) {
        stream << get_indent() << name << "(\n";
        indent_level++;
        std::string comma = "";
        for (auto *p : v) {
            std::string c_type = p->get_c_type();
            if (c_type == "AutoschedulerParams") {
                c_type = "const AutoschedulerParams&";
            }
            stream << get_indent() << comma << c_type << " " << p->name() << "\n";
            comma = ", ";
        }
        indent_level--;
        stream << get_indent() << ") : \n";
        indent_level++;
        comma = "";
        for (auto *p : v) {
            stream << get_indent() << comma << p->name() << "(" << p->name() << ")\n";
            comma = ", ";
        }
        indent_level--;
        stream << get_indent() << "{\n";
        stream << get_indent() << "}\n";
        stream << "\n";
    }

    indent_level--;
    stream << get_indent() << "};\n";
    stream << "\n";
}

void StubEmitter::emit_inputs_struct() {
    struct InInfo {
        std::string c_type;
        std::string name;
    };
    std::vector<InInfo> in_info;
    for (auto *input : inputs) {
        std::stringstream c_type;
        if (input->is_array()) {
            c_type << "std::vector<";
        }
        c_type << input->get_c_type();
        if (input->is_array()) {
            c_type << ">";
        }
        in_info.push_back({c_type.str(), input->name()});
    }

    const std::string name = "Inputs";
    stream << get_indent() << "struct " << name << " final {\n";
    indent_level++;
    for (const auto &in : in_info) {
        stream << get_indent() << in.c_type << " " << in.name << ";\n";
    }
    stream << "\n";

    stream << get_indent() << name << "() {}\n";
    stream << "\n";
    if (!in_info.empty()) {
        stream << get_indent() << name << "(\n";
        indent_level++;
        std::string comma = "";
        for (const auto &in : in_info) {
            stream << get_indent() << comma << "const " << in.c_type << "& " << in.name << "\n";
            comma = ", ";
        }
        indent_level--;
        stream << get_indent() << ") : \n";
        indent_level++;
        comma = "";
        for (const auto &in : in_info) {
            stream << get_indent() << comma << in.name << "(" << in.name << ")\n";
            comma = ", ";
        }
        indent_level--;
        stream << get_indent() << "{\n";
        stream << get_indent() << "}\n";

        indent_level--;
    }
    stream << get_indent() << "};\n";
    stream << "\n";
}

void StubEmitter::emit() {
    if (outputs.empty()) {
        // The generator can't support a real stub. Instead, generate an (essentially)
        // empty .stub.h file, so that build systems like Bazel will still get the output file
        // they expected. Note that we deliberately don't emit an ifndef header guard,
        // since we can't reliably assume that the generator_name will be globally unique;
        // on the other hand, since this file is just a couple of comments, it's
        // really not an issue if it's included multiple times.
        stream << "/* MACHINE-GENERATED - DO NOT EDIT */\n";
        stream << "/* The Generator named " << generator_registered_name << " uses ImageParam or Param, thus cannot have a Stub generated. */\n";
        return;
    }

    struct OutputInfo {
        std::string name;
        std::string ctype;
        std::string getter;
    };
    bool all_outputs_are_func = true;
    std::vector<OutputInfo> out_info;
    for (auto *output : outputs) {
        std::string c_type = output->get_c_type();
        const bool is_func = (c_type == "Func");
        std::stringstream getter;

        if (!is_func) {
            getter << c_type << "::to_output_buffers(";
        }
        getter << "generator->output_func(\"" << output->name() << "\")";
        if (!is_func) {
            getter << ", generator)";
        }
        if (!output->is_array()) {
            getter << ".at(0)";
        }

        out_info.push_back({output->name(),
                            output->is_array() ? "std::vector<" + c_type + ">" : c_type,
                            getter.str()});
        if (c_type != "Func") {
            all_outputs_are_func = false;
        }
    }

    std::ostringstream guard;
    guard << "HALIDE_STUB";
    for (const auto &ns : namespaces) {
        guard << "_" << ns;
    }
    guard << "_" << class_name;

    stream << get_indent() << "#ifndef " << guard.str() << "\n";
    stream << get_indent() << "#define " << guard.str() << "\n";
    stream << "\n";

    stream << get_indent() << "/* MACHINE-GENERATED - DO NOT EDIT */\n";
    stream << "\n";

    stream << get_indent() << "#include <cassert>\n";
    stream << get_indent() << "#include <iterator>\n";
    stream << get_indent() << "#include <map>\n";
    stream << get_indent() << "#include <memory>\n";
    stream << get_indent() << "#include <string>\n";
    stream << get_indent() << "#include <utility>\n";
    stream << get_indent() << "#include <vector>\n";
    stream << "\n";
    stream << get_indent() << "#include \"Halide.h\"\n";
    stream << "\n";

    stream << "namespace halide_register_generator {\n";
    stream << "namespace " << generator_registered_name << "_ns {\n";
    stream << "extern std::unique_ptr<Halide::Internal::AbstractGenerator> factory(const Halide::GeneratorContext& context);\n";
    stream << "}  // namespace halide_register_generator\n";
    stream << "}  // namespace " << generator_registered_name << "\n";
    stream << "\n";

    for (const auto &ns : namespaces) {
        stream << get_indent() << "namespace " << ns << " {\n";
    }
    stream << "\n";

    for (auto *p : generator_params) {
        std::string decl = p->get_type_decls();
        if (decl.empty()) {
            continue;
        }
        stream << decl << "\n";
    }

    stream << get_indent() << "class " << class_name << " final : public Halide::NamesInterface {\n";
    stream << get_indent() << "public:\n";
    indent_level++;

    emit_inputs_struct();
    emit_generator_params_struct();

    stream << get_indent() << "struct Outputs final {\n";
    indent_level++;
    stream << get_indent() << "// Outputs\n";
    for (const auto &out : out_info) {
        stream << get_indent() << out.ctype << " " << out.name << ";\n";
    }

    stream << "\n";
    stream << get_indent() << "// The Target used\n";
    stream << get_indent() << "Target target;\n";

    if (out_info.size() == 1) {
        stream << "\n";
        if (all_outputs_are_func) {
            std::string name = out_info.at(0).name;
            auto *output = outputs[0];
            if (output->is_array()) {
                stream << get_indent() << "operator std::vector<Halide::Func>() const {\n";
                indent_level++;
                stream << get_indent() << "return " << name << ";\n";
                indent_level--;
                stream << get_indent() << "}\n";

                stream << get_indent() << "Halide::Func operator[](size_t i) const {\n";
                indent_level++;
                stream << get_indent() << "return " << name << "[i];\n";
                indent_level--;
                stream << get_indent() << "}\n";

                stream << get_indent() << "Halide::Func at(size_t i) const {\n";
                indent_level++;
                stream << get_indent() << "return " << name << ".at(i);\n";
                indent_level--;
                stream << get_indent() << "}\n";

                stream << get_indent() << "// operator operator()() overloads omitted because the sole Output is array-of-Func.\n";
            } else {
                // If there is exactly one output, add overloads
                // for operator Func and operator().
                stream << get_indent() << "operator Halide::Func() const {\n";
                indent_level++;
                stream << get_indent() << "return " << name << ";\n";
                indent_level--;
                stream << get_indent() << "}\n";

                stream << "\n";
                stream << get_indent() << "template <typename... Args>\n";
                stream << get_indent() << "Halide::FuncRef operator()(Args&&... args) const {\n";
                indent_level++;
                stream << get_indent() << "return " << name << "(std::forward<Args>(args)...);\n";
                indent_level--;
                stream << get_indent() << "}\n";

                stream << "\n";
                stream << get_indent() << "template <typename ExprOrVar>\n";
                stream << get_indent() << "Halide::FuncRef operator()(std::vector<ExprOrVar> args) const {\n";
                indent_level++;
                stream << get_indent() << "return " << name << "()(args);\n";
                indent_level--;
                stream << get_indent() << "}\n";
            }
        } else {
            stream << get_indent() << "// operator Func() and operator()() overloads omitted because the sole Output is not Func.\n";
        }
    }

    stream << "\n";
    if (all_outputs_are_func) {
        stream << get_indent() << "Halide::Pipeline get_pipeline() const {\n";
        indent_level++;
        stream << get_indent() << "return Halide::Pipeline(std::vector<Halide::Func>{\n";
        indent_level++;
        int commas = (int)out_info.size() - 1;
        for (const auto &out : out_info) {
            stream << get_indent() << out.name << (commas-- ? "," : "") << "\n";
        }
        indent_level--;
        stream << get_indent() << "});\n";
        indent_level--;
        stream << get_indent() << "}\n";

        stream << "\n";
        stream << get_indent() << "Halide::Realization realize(std::vector<int32_t> sizes) {\n";
        indent_level++;
        stream << get_indent() << "return get_pipeline().realize(sizes, target);\n";
        indent_level--;
        stream << get_indent() << "}\n";

        stream << "\n";
        stream << get_indent() << "template <typename... Args, typename std::enable_if<Halide::Internal::NoRealizations<Args...>::value>::type * = nullptr>\n";
        stream << get_indent() << "Halide::Realization realize(Args&&... args) {\n";
        indent_level++;
        stream << get_indent() << "return get_pipeline().realize(std::forward<Args>(args)..., target);\n";
        indent_level--;
        stream << get_indent() << "}\n";

        stream << "\n";
        stream << get_indent() << "void realize(Halide::Realization r) {\n";
        indent_level++;
        stream << get_indent() << "get_pipeline().realize(r, target);\n";
        indent_level--;
        stream << get_indent() << "}\n";
    } else {
        stream << get_indent() << "// get_pipeline() and realize() overloads omitted because some Outputs are not Func.\n";
    }

    indent_level--;
    stream << get_indent() << "};\n";
    stream << "\n";

    stream << get_indent() << "HALIDE_NO_USER_CODE_INLINE static Outputs generate(\n";
    indent_level++;
    stream << get_indent() << "const GeneratorContext& context,\n";
    stream << get_indent() << "const Inputs& inputs,\n";
    stream << get_indent() << "const GeneratorParams& generator_params = GeneratorParams()\n";
    indent_level--;
    stream << get_indent() << ")\n";
    stream << get_indent() << "{\n";
    indent_level++;
    stream << get_indent() << "std::shared_ptr<Halide::Internal::AbstractGenerator> generator = halide_register_generator::" << generator_registered_name << "_ns::factory(context);\n";
    for (auto *p : generator_params) {
        stream << get_indent();
        if (p->is_looplevel_param()) {
            stream << "generator->set_generatorparam_value(";
        } else {
            stream << "generator->set_generatorparam_value(";
        }
        stream << "\"" << p->name() << "\", ";
        if (p->is_looplevel_param()) {
            stream << "generator_params." << p->name();
        } else {
            stream << p->call_to_string("generator_params." + p->name());
        }
        stream << ");\n";
    }

    for (auto *p : inputs) {
        stream << get_indent() << "generator->bind_input("
               << "\"" << p->name() << "\", ";
        if (p->kind() == ArgInfoKind::Buffer) {
            stream << "Halide::Internal::StubInputBuffer<>::to_parameter_vector(inputs." << p->name() << ")";
        } else {
            // Func or Expr
            if (!p->is_array()) {
                stream << "{";
            }
            stream << "inputs." << p->name();
            if (!p->is_array()) {
                stream << "}";
            }
        }
        stream << ");\n";
    }

    stream << get_indent() << "generator->build_pipeline();\n";
    stream << get_indent() << "return {\n";
    indent_level++;
    for (const auto &out : out_info) {
        stream << get_indent() << out.getter << ",\n";
    }
    stream << get_indent() << "generator->context().target()\n";
    indent_level--;
    stream << get_indent() << "};\n";
    indent_level--;
    stream << get_indent() << "}\n";
    stream << "\n";

    stream << get_indent() << "// overload to allow GeneratorBase-pointer\n";
    stream << get_indent() << "inline static Outputs generate(\n";
    indent_level++;
    stream << get_indent() << "const Halide::Internal::GeneratorBase* generator,\n";
    stream << get_indent() << "const Inputs& inputs,\n";
    stream << get_indent() << "const GeneratorParams& generator_params = GeneratorParams()\n";
    indent_level--;
    stream << get_indent() << ")\n";
    stream << get_indent() << "{\n";
    indent_level++;
    stream << get_indent() << "return generate(generator->context(), inputs, generator_params);\n";
    indent_level--;
    stream << get_indent() << "}\n";
    stream << "\n";

    stream << get_indent() << "// overload to allow Target instead of GeneratorContext.\n";
    stream << get_indent() << "inline static Outputs generate(\n";
    indent_level++;
    stream << get_indent() << "const Target& target,\n";
    stream << get_indent() << "const Inputs& inputs,\n";
    stream << get_indent() << "const GeneratorParams& generator_params = GeneratorParams()\n";
    indent_level--;
    stream << get_indent() << ")\n";
    stream << get_indent() << "{\n";
    indent_level++;
    stream << get_indent() << "return generate(Halide::GeneratorContext(target), inputs, generator_params);\n";
    indent_level--;
    stream << get_indent() << "}\n";
    stream << "\n";

    stream << get_indent() << class_name << "() = delete;\n";

    indent_level--;
    stream << get_indent() << "};\n";
    stream << "\n";

    for (const auto &ns : reverse_view(namespaces)) {
        stream << get_indent() << "}  // namespace " << ns << "\n";
    }
    stream << "\n";

    stream << get_indent() << "#endif  // " << guard.str() << "\n";
}

const std::map<std::string, Type> &get_halide_type_enum_map() {
    static const std::map<std::string, Type> halide_type_enum_map{
        {"bool", Bool()},
        {"int8", Int(8)},
        {"int16", Int(16)},
        {"int32", Int(32)},
        {"int64", Int(64)},
        {"uint8", UInt(8)},
        {"uint16", UInt(16)},
        {"uint32", UInt(32)},
        {"uint64", UInt(64)},
        {"float16", Float(16)},
        {"float32", Float(32)},
        {"float64", Float(64)},
        {"bfloat16", BFloat(16)}};
    return halide_type_enum_map;
}

std::string halide_type_to_c_source(const Type &t) {
    static const std::map<halide_type_code_t, std::string> m = {
        {halide_type_int, "Int"},
        {halide_type_uint, "UInt"},
        {halide_type_float, "Float"},
        {halide_type_handle, "Handle"},
    };
    std::ostringstream oss;
    oss << "Halide::" << m.at(t.code()) << "(" << t.bits() << +")";
    return oss.str();
}

std::string halide_type_to_c_type(const Type &t) {
    auto encode = [](const Type &t) -> int { return t.code() << 16 | t.bits(); };
    static const std::map<int, std::string> m = {
        {encode(Int(8)), "int8_t"},
        {encode(Int(16)), "int16_t"},
        {encode(Int(32)), "int32_t"},
        {encode(Int(64)), "int64_t"},
        {encode(UInt(1)), "bool"},
        {encode(UInt(8)), "uint8_t"},
        {encode(UInt(16)), "uint16_t"},
        {encode(UInt(32)), "uint32_t"},
        {encode(UInt(64)), "uint64_t"},
        {encode(BFloat(16)), "uint16_t"},  // TODO: see Issues #3709, #3967
        {encode(Float(16)), "uint16_t"},   // TODO: see Issues #3709, #3967
        {encode(Float(32)), "float"},
        {encode(Float(64)), "double"},
        {encode(Handle(64)), "void*"}};
    internal_assert(m.count(encode(t))) << t << " " << encode(t);
    return m.at(encode(t));
}

namespace {

int generate_filter_main_inner(int argc,
                               char **argv,
                               const GeneratorFactoryProvider &generator_factory_provider) {
    static const char kUsage[] = R"INLINE_CODE(
gengen
  [-g GENERATOR_NAME] [-f FUNCTION_NAME] [-o OUTPUT_DIR] [-r RUNTIME_NAME]
  [-d 1|0] [-e EMIT_OPTIONS] [-n FILE_BASE_NAME] [-p PLUGIN_NAME]
  [-s AUTOSCHEDULER_NAME] [-t TIMEOUT]
  target=target-string[,target-string...]
  [generator_param=value [...]]

 -d  Build a module that is suitable for using for gradient descent calculation
     in TensorFlow or PyTorch. See Generator::build_gradient_module()
     documentation.

 -e  A comma separated list of files to emit. Accepted values are:
     [assembly, bitcode, c_header, c_source, cpp_stub, featurization,
      llvm_assembly, object, python_extension, pytorch_wrapper, registration,
      schedule, static_library, stmt, stmt_html, conceptual_stmt,
      conceptual_stmt_html, compiler_log, hlpipe, device_code].
     If omitted, default value is [c_header, static_library, registration].

 -p  A comma-separated list of shared libraries that will be loaded before the
     generator is run. Useful for custom auto-schedulers. The generator must
     either be linked against a shared libHalide or compiled with -rdynamic
     so that references in the shared library to libHalide can resolve.
     (Note that this does not change the default autoscheduler; use the -s flag
     to set that value.)"

 -r  The name of a standalone runtime to generate. Only honors EMIT_OPTIONS 'o'
     and 'static_library'. When multiple targets are specified, it picks a
     runtime that is compatible with all of the targets, or fails if it cannot
     find one. Flags across all of the targets that do not affect runtime code
     generation, such as `no_asserts` and `no_runtime`, are ignored.

 -t  Timeout for the Generator to run, in seconds; mainly useful to ensure that
     bugs and/or degenerate cases don't stall build systems. Specify 0 to allow
     infinite time. Defaults to infinite.

 -v  If nonzero, log the path to all generated files to stdout.
)INLINE_CODE";

    std::map<std::string, std::string> flags_info = {
        {"-d", "0"},
        {"-e", ""},
        {"-f", ""},
        {"-g", ""},
        {"-n", ""},
        {"-o", ""},
        {"-p", ""},
        {"-r", ""},
        {"-v", "0"},
        {"-t", "0"},
    };

    ExecuteGeneratorArgs args;

    for (int i = 1; i < argc; ++i) {
        if (argv[i][0] != '-') {
            std::vector<std::string> v = split_string(argv[i], "=");
            user_assert(v.size() == 2 && !v[0].empty() && !v[1].empty()) << kUsage;
            args.generator_params[v[0]] = v[1];
        } else if (auto it = flags_info.find(argv[i]); it != flags_info.end()) {
            user_assert(i + 1 < argc) << kUsage;
            it->second = argv[i + 1];
            ++i;
            continue;
        } else {
            if (!strcmp(argv[i], "-s")) {
                user_error << "-s is no longer supported for setting autoscheduler; specify autoschduler.name=NAME instead.\n"
                           << kUsage;
            }
            user_error << "Unknown flag: " << argv[i] << "\n"
                       << kUsage;
        }
    }

    // It's possible that in the future loaded plugins might change
    // how arguments are parsed, so we handle those first.
    for (const auto &lib_path : split_string(flags_info["-p"], ",")) {
        if (!lib_path.empty()) {
            load_plugin(lib_path);
        }
    }

    if (args.generator_params.count("auto_schedule")) {
        user_error << "auto_schedule=true is no longer supported for enabling autoscheduling; specify autoscheduler=NAME instead.\n"
                   << kUsage;
    }
    if (args.generator_params.count("machine_params")) {
        user_error << "machine_params is no longer supported as a GeneratorParam; specify autoscheduler.FIELD=VALUE instead.\n"
                   << kUsage;
    }

    const auto &d_val = flags_info["-d"];
    user_assert(d_val == "1" || d_val == "0") << "-d must be 0 or 1\n"
                                              << kUsage;

    const auto &v_val = flags_info["-v"];
    user_assert(v_val == "1" || v_val == "0") << "-v must be 0 or 1\n"
                                              << kUsage;

    const std::vector<std::string> generator_names = generator_factory_provider.enumerate();

    const auto create_generator = [&](const std::string &generator_name, const Halide::GeneratorContext &context) -> AbstractGeneratorPtr {
        internal_assert(generator_name == args.generator_name);
        auto g = generator_factory_provider.create(generator_name, context);
        if (!g) {
            std::ostringstream o;
            o << "Generator not found: " << generator_name << "\n";
            o << "Did you mean:\n";
            for (const auto &n : generator_names) {
                o << "    " << n << "\n";
            }
            user_error << o.str();
        }
        return g;
    };

    const auto build_target_strings = [](GeneratorParamsMap *gp) {
        std::vector<std::string> target_strings;
        if (gp->find("target") != gp->end()) {
            target_strings = split_string((*gp)["target"], ",");
            gp->erase("target");
        }
        return target_strings;
    };

    const auto build_targets = [](const std::vector<std::string> &target_strings) {
        std::vector<Target> targets;
        targets.reserve(target_strings.size());
        for (const auto &s : target_strings) {
            targets.emplace_back(s);
        }
        return targets;
    };

    const auto build_output_types = [&]() {
        std::set<OutputFileType> output_types;

        std::string emit_flags_string = flags_info["-e"];

        // If omitted or empty, assume .a and .h and registration.cpp
        if (emit_flags_string.empty()) {
            emit_flags_string = "c_header,registration,static_library";
        }

        // If HL_EXTRA_OUTPUTS is defined, assume it's extra outputs we want to generate
        // (usually for temporary debugging purposes) and just tack it on to the -e contents.
        std::string extra_outputs = get_env_variable("HL_EXTRA_OUTPUTS");
        if (!extra_outputs.empty()) {
            if (!emit_flags_string.empty()) {
                emit_flags_string += ",";
            }
            emit_flags_string += extra_outputs;
        }

        const std::vector<std::string> emit_flags = split_string(emit_flags_string, ",");
        internal_assert(!emit_flags.empty()) << "Empty emit flags.\n";

        // Build a reverse lookup table. Allow some legacy aliases on the command line,
        // to allow legacy build systems to work more easily.
        std::map<std::string, OutputFileType> output_name_to_enum = {
            {"cpp", OutputFileType::c_source},
            {"h", OutputFileType::c_header},
            {"hlpipe", OutputFileType::hlpipe},
            {"html", OutputFileType::stmt_html},
            {"o", OutputFileType::object},
            {"py.c", OutputFileType::python_extension},
        };
        // extensions won't vary across multitarget output
        const Target t = args.targets.empty() ? Target() : args.targets[0];
        const std::map<OutputFileType, const OutputInfo> output_info = get_output_info(t);
        for (const auto &it : output_info) {
            output_name_to_enum[it.second.name] = it.first;
        }

        for (const std::string &opt : emit_flags) {
            auto it = output_name_to_enum.find(opt);
            if (it == output_name_to_enum.end()) {
                std::ostringstream o;
                o << "Unrecognized emit option: " << opt << " is not one of [";
                auto end = output_info.cend();
                auto last = std::prev(end);
                for (auto iter = output_info.cbegin(); iter != end; ++iter) {
                    o << iter->second.name;
                    if (iter != last) {
                        o << " ";
                    }
                }
                o << "], ignoring.\n";
                o << kUsage;
                user_error << o.str();
            }
            output_types.insert(it->second);
        }

        return output_types;
    };

    // Always specify target_strings for suffixes: if we omit this, we'll use *canonical* target strings
    // for suffixes, but our caller might have passed non-canonical-but-still-legal target strings,
    // and if we don't use those, the output filenames might not match what the caller expects.
    args.suffixes = build_target_strings(&args.generator_params);
    args.targets = build_targets(args.suffixes);
    args.output_dir = flags_info["-o"];
    args.output_types = build_output_types();
    args.generator_name = flags_info["-g"];
    args.function_name = flags_info["-f"];
    args.file_base_name = flags_info["-n"];
    args.runtime_name = flags_info["-r"];
    args.build_mode = (d_val == "1") ? ExecuteGeneratorArgs::Gradient : ExecuteGeneratorArgs::Default;
    args.create_generator = create_generator;
    // args.generator_params is already set
    // If true, log the path of all output files to stdout.
    args.log_outputs = (v_val == "1");

    // Allow quick-n-dirty use of compiler logging via HL_DEBUG_COMPILER_LOGGER env var
    const bool do_compiler_logging = args.output_types.count(OutputFileType::compiler_log) ||
                                     (get_env_variable("HL_DEBUG_COMPILER_LOGGER") == "1");
    if (do_compiler_logging) {
        const bool obfuscate_compiler_logging = get_env_variable("HL_OBFUSCATE_COMPILER_LOGGER") == "1";
        args.compiler_logger_factory =
            [obfuscate_compiler_logging, &args](const std::string &function_name, const Target &target) -> std::unique_ptr<CompilerLogger> {
            // rebuild generator_args from the map so that they are always canonical
            std::stringstream generator_args_string;
            std::string autoscheduler_name;
            std::string sep;
            for (const auto &it : args.generator_params) {
                std::string quote = it.second.find(' ') != std::string::npos ? "\\\"" : "";
                generator_args_string << sep << it.first << "=" << quote << it.second << quote;
                sep = " ";
                if (it.first == "autoscheduler") {
                    autoscheduler_name = it.second;
                }
            }
            std::unique_ptr<JSONCompilerLogger> t(new JSONCompilerLogger(
                obfuscate_compiler_logging ? "" : args.generator_name,
                obfuscate_compiler_logging ? "" : args.function_name,
                obfuscate_compiler_logging ? "" : autoscheduler_name,
                obfuscate_compiler_logging ? Target() : target,
                obfuscate_compiler_logging ? "" : generator_args_string.str(),
                obfuscate_compiler_logging));
            return t;
        };
    }

    // Do some preflighting here to emit errors that are likely from the command line
    // but not necessarily from the API call.
    user_assert(!(generator_names.empty() && args.runtime_name.empty()))
        << "No generators have been registered and not compiling a standalone runtime\n"
        << kUsage;

    if (args.generator_name.empty() && args.runtime_name.empty()) {
        // Require at least one of -g or -r to be specified.
        std::ostringstream o;
        o << "Either -g <name> or -r must be specified; available Generators are:\n";
        if (!generator_names.empty()) {
            for (const auto &name : generator_names) {
                o << "    " << name << "\n";
            }
        } else {
            o << "    <none>\n";
        }
        user_error << o.str();
    }

    execute_generator(args);
    return 0;
}

class GeneratorsFromRegistry : public GeneratorFactoryProvider {
public:
    GeneratorsFromRegistry() = default;
    ~GeneratorsFromRegistry() override = default;

    std::vector<std::string> enumerate() const override {
        return GeneratorRegistry::enumerate();
    }

    AbstractGeneratorPtr create(const std::string &name,
                                const Halide::GeneratorContext &context) const override {
        return GeneratorRegistry::create(name, context);
    }
};

}  // namespace

const GeneratorFactoryProvider &get_registered_generators() {
    static GeneratorsFromRegistry g;
    return g;
}

}  // namespace Internal

Callable create_callable_from_generator(const GeneratorContext &context,
                                        const std::string &name,
                                        const GeneratorParamsMap &generator_params) {
    auto g = Internal::get_registered_generators().create(name, context);
    user_assert(g != nullptr) << "There is no Generator with the name '" << name << "' currently available.";
    g->set_generatorparam_values(generator_params);
    return g->compile_to_callable();
}

Callable create_callable_from_generator(const Target &target,
                                        const std::string &name,
                                        const GeneratorParamsMap &generator_params) {
    return create_callable_from_generator(GeneratorContext(target), name, generator_params);
}

namespace Internal {

#ifdef HALIDE_WITH_EXCEPTIONS
int generate_filter_main(int argc, char **argv, const GeneratorFactoryProvider &generator_factory_provider) {
    try {
        return generate_filter_main_inner(argc, argv, generator_factory_provider);
    } catch (::Halide::Error &err) {
        // Do *not* use user_error here (or elsewhere in this function): it
        // will throw an exception, and since there is almost certainly no
        // try/catch block in our caller, it will call std::terminate,
        // swallowing all error messages.
        std::cerr << "Unhandled exception: " << err.what() << "\n";
        return -1;
    } catch (std::exception &err) {
        std::cerr << "Unhandled exception: " << err.what() << "\n";
        return -1;
    } catch (...) {
        std::cerr << "Unhandled exception: (unknown)\n";
        return -1;
    }
}
#else
int generate_filter_main(int argc, char **argv, const GeneratorFactoryProvider &generator_factory_provider) {
    return generate_filter_main_inner(argc, argv, generator_factory_provider);
}
#endif

int generate_filter_main(int argc, char **argv) {
    return generate_filter_main(argc, argv, GeneratorsFromRegistry());
}

void execute_generator(const ExecuteGeneratorArgs &args_in) {
    const auto fix_defaults = [](const ExecuteGeneratorArgs &args_in) -> ExecuteGeneratorArgs {
        ExecuteGeneratorArgs args = args_in;
        if (!args.create_generator) {
            args.create_generator = [](const std::string &generator_name, const GeneratorContext &context) -> AbstractGeneratorPtr {
                return GeneratorRegistry::create(generator_name, context);
            };
        }
        if (!args.compiler_logger_factory) {
            args.compiler_logger_factory = [](const std::string &, const Target &) -> std::unique_ptr<CompilerLogger> {
                return nullptr;
            };
        }
        if (args.function_name.empty()) {
            args.function_name = args.generator_name;
        }
        if (args.file_base_name.empty()) {
            args.file_base_name = strip_namespaces(args.function_name);
        }
        return args;
    };

    const ExecuteGeneratorArgs args = fix_defaults(args_in);

    // -------------- Do some sanity checking.
    internal_assert(!args.output_dir.empty());

    const bool cpp_stub_only = args.output_types.size() == 1 &&
                               args.output_types.count(OutputFileType::cpp_stub) == 1;

    if (!cpp_stub_only) {
        // It's ok to leave targets unspecified if we are generating *only* a cpp_stub
        internal_assert(!args.targets.empty());
    }

    const auto ensure_valid_name = [](const std::string &s) {
        internal_assert(s.empty() || is_valid_name(s)) << "string '" << s << "' is not a valid Generator name.";
    };
    const auto ensure_not_pathname = [](const std::string &s) {
        for (char c : "/\\") {
            internal_assert(s.find(c) == std::string::npos) << "string '" << s << "' must not contain '" << c << "', but saw '" << s << "'";
        }
    };

    // These should be valid Generator names by the rules of is_valid_name()
    ensure_valid_name(args.generator_name);

    // These should be valid "leaf" filenames, but not full or partial pathnames
    ensure_not_pathname(args.runtime_name);
    ensure_not_pathname(args.function_name);
    ensure_not_pathname(args.file_base_name);
    for (const auto &s : args.suffixes) {
        ensure_not_pathname(s);
    }

    // -------------- Process the arguments.

    if (!args.runtime_name.empty()) {
        // Runtime always ignores file_base_name
        const std::string base_path = args.output_dir + "/" + args.runtime_name;

        Target gcd_target = args.targets[0];
        for (size_t i = 1; i < args.targets.size(); i++) {
            internal_assert(gcd_target.get_runtime_compatible_target(args.targets[i], gcd_target))
                << "Failed to find compatible runtime target for " << gcd_target << " and " << args.targets[i];
        }

        if (args.targets.size() > 1) {
            debug(1) << "Building runtime for computed target: " << gcd_target << "\n";
        }

        auto output_files = compute_output_files(gcd_target, base_path, args.output_types);
        // Runtime doesn't get to participate in the CompilerLogger party
        compile_standalone_runtime(output_files, gcd_target);
    }

    if (!args.generator_name.empty()) {
        const std::string base_path = args.output_dir + "/" + args.file_base_name;
        debug(1) << "Generator " << args.generator_name << " has base_path " << base_path << "\n";

        // Factory function for creating a generator instance for a given function name and target
        auto generator_factory = [&](const std::string &function_name, const Target &target) -> AbstractGeneratorPtr {
            // Must re-create each time since each instance will have a different Target.
            auto gen = args.create_generator(args.generator_name, GeneratorContext(target));
            for (const auto &kv : args.generator_params) {
                if (kv.first == "target") {
                    continue;
                }
                gen->set_generatorparam_value(kv.first, kv.second);
            }
            return gen;
        };

        if (args.output_types.count(OutputFileType::cpp_stub)) {
            // When generating cpp_stub we ignore all generator args passed in, and supply a fake Target.
            // (CompilerLogger is never enabled for cpp_stub, for now anyway.)
            const Target fake_target = Target();
            auto gen = args.create_generator(args.generator_name, GeneratorContext(fake_target));
            auto output_files = compute_output_files(fake_target, base_path, args.output_types);
            gen->emit_cpp_stub(output_files[OutputFileType::cpp_stub]);
        }

#ifdef WITH_SERIALIZATION
        if (args.output_types.count(OutputFileType::hlpipe)) {
            // When serializing a halide pipeline, target is required (since the schedule may be target dependent).
            // If multiple targets are specified, add the target name as a suffix to the filename.
            const bool use_target_suffix = (args.targets.size() > 1);
            for (size_t i = 0; i < args.targets.size(); ++i) {
                const Target &target = args.targets[i];
                const std::string hlpipe_path = use_target_suffix ? (base_path + "-" + target.to_string()) : base_path;
                auto output_files = compute_output_files(target, hlpipe_path, args.output_types);
                auto gen = generator_factory(args.function_name, target);
                gen->emit_hlpipe(output_files[OutputFileType::hlpipe]);
            }
        }
#endif

        // Don't bother with this if we're just emitting a cpp_stub.
        if (!cpp_stub_only) {
            auto output_files = compute_output_files(args.targets[0], base_path, args.output_types);
            auto module_factory = [&](const std::string &function_name, const Target &target) -> Module {
                auto gen = generator_factory(function_name, target);
                return args.build_mode == ExecuteGeneratorArgs::Gradient ?
                           gen->build_gradient_module(function_name) :
                           gen->build_module(function_name);
            };
            compile_multitarget(args.function_name, output_files, args.targets, args.suffixes, module_factory, args.compiler_logger_factory);
            if (args.log_outputs) {
                for (const auto &o : output_files) {
                    std::cout << "Generated file: " << o.second << "\n";
                }
            }
        }
    }
}

GeneratorParamBase::GeneratorParamBase(const std::string &name)
    : name_(name) {
    ObjectInstanceRegistry::register_instance(this, 0, ObjectInstanceRegistry::GeneratorParam, this);
}

GeneratorParamBase::~GeneratorParamBase() {
    ObjectInstanceRegistry::unregister_instance(this);
}

void GeneratorParamBase::check_value_readable() const {
    // These are always readable.
    if (name() == "target" ||
        name() == "autoscheduler") {
        return;
    }
    user_assert(generator && generator->phase >= GeneratorBase::ConfigureCalled)
        << "The GeneratorParam \"" << name() << "\" cannot be read before configure()/generate() is called.\n";
}

void GeneratorParamBase::check_value_writable() const {
    // Allow writing when no Generator is set, to avoid having to special-case ctor initing code
    if (!generator) {
        return;
    }
    user_assert(generator->phase < GeneratorBase::GenerateCalled)
        << "The GeneratorParam \"" << name() << "\" cannot be written after generate() is called.\n";
}

void GeneratorParamBase::fail_wrong_type(const char *type) {
    user_error << "The GeneratorParam \"" << name() << "\" cannot be set with a value of type " << type << ".\n";
}

GeneratorParam_AutoSchedulerParams::GeneratorParam_AutoSchedulerParams()
    : GeneratorParamImpl<AutoschedulerParams>("autoscheduler", {}) {
}

void GeneratorParam_AutoSchedulerParams::set_from_string(const std::string &new_value_string) {
    internal_error << "This method should never be called.";
}

std::string GeneratorParam_AutoSchedulerParams::get_default_value() const {
    internal_error << "This method should never be called.";
    return "";
}

std::string GeneratorParam_AutoSchedulerParams::call_to_string(const std::string &v) const {
    internal_error << "This method should never be called.";
    return "";
}

std::string GeneratorParam_AutoSchedulerParams::get_c_type() const {
    internal_error << "This method should never be called.";
    return "";
}

bool GeneratorParam_AutoSchedulerParams::try_set(const std::string &key, const std::string &value) {
    const auto &n = this->name();
    if (key == n) {
        user_assert(this->value_.name.empty()) << "The GeneratorParam " << key << " cannot be set more than once.\n";
        this->value_.name = value;
        return true;
    } else if (starts_with(key, n + ".")) {
        const auto sub_key = key.substr(n.size() + 1);
        user_assert(this->value_.extra.count(sub_key) == 0) << "The GeneratorParam " << key << " cannot be set more than once.\n";
        this->value_.extra[sub_key] = value;
        return true;
    } else {
        return false;
    }
}

/* static */
GeneratorRegistry &GeneratorRegistry::get_registry() {
    static GeneratorRegistry *registry = new GeneratorRegistry;
    return *registry;
}

/* static */
void GeneratorRegistry::register_factory(const std::string &name,
                                         GeneratorFactory generator_factory) {
    user_assert(is_valid_name(name)) << "Invalid Generator name: " << name;
    GeneratorRegistry &registry = get_registry();
    std::scoped_lock lock(registry.mutex);
    internal_assert(registry.factories.find(name) == registry.factories.end())
        << "Duplicate Generator name: " << name;
    registry.factories[name] = std::move(generator_factory);
}

/* static */
void GeneratorRegistry::unregister_factory(const std::string &name) {
    GeneratorRegistry &registry = get_registry();
    std::scoped_lock lock(registry.mutex);
    internal_assert(registry.factories.find(name) != registry.factories.end())
        << "Generator not found: " << name;
    registry.factories.erase(name);
}

/* static */
AbstractGeneratorPtr GeneratorRegistry::create(const std::string &name,
                                               const GeneratorContext &context) {
    GeneratorRegistry &registry = get_registry();
    std::scoped_lock lock(registry.mutex);
    auto it = registry.factories.find(name);
    if (it == registry.factories.end()) {
        return nullptr;
    }
    GeneratorFactory f = it->second;
    AbstractGeneratorPtr g = f(context);
    // Do not assert! Just return nullptr.
    // internal_assert(g != nullptr);
    return g;
}

/* static */
std::vector<std::string> GeneratorRegistry::enumerate() {
    GeneratorRegistry &registry = get_registry();
    std::scoped_lock lock(registry.mutex);
    std::vector<std::string> result;
    result.reserve(registry.factories.size());
    for (const auto &i : registry.factories) {
        result.push_back(i.first);
    }
    return result;
}

GeneratorBase::GeneratorBase(size_t size)
    : size(size) {
    ObjectInstanceRegistry::register_instance(this, size, ObjectInstanceRegistry::Generator, this);
}

GeneratorBase::~GeneratorBase() {
    ObjectInstanceRegistry::unregister_instance(this);
}

GeneratorParamInfo::GeneratorParamInfo(GeneratorBase *generator, const size_t size) {
    const auto add_synthetic_params = [this, generator](GIOBase *gio) {
        const std::string &n = gio->name();
        const std::string &gn = generator->generator_registered_name;

        owned_synthetic_params.push_back(GeneratorParam_Synthetic<Type>::make(generator, gn, n + ".type", *gio, SyntheticParamType::Type, gio->gio_types_defined()));
        filter_generator_params.push_back(owned_synthetic_params.back().get());

        if (gio->kind() != ArgInfoKind::Scalar) {
            owned_synthetic_params.push_back(GeneratorParam_Synthetic<int>::make(generator, gn, n + ".dim", *gio, SyntheticParamType::Dim, gio->dims_defined()));
            filter_generator_params.push_back(owned_synthetic_params.back().get());
        }
        if (gio->is_array()) {
            owned_synthetic_params.push_back(GeneratorParam_Synthetic<size_t>::make(generator, gn, n + ".size", *gio, SyntheticParamType::ArraySize, gio->array_size_defined()));
            filter_generator_params.push_back(owned_synthetic_params.back().get());
        }
    };

    const char *const io_order_warning = "Generators will always produce code that orders all Inputs before all Outputs; "
                                         "this Generator declares the Inputs and Outputs in a different order, so the calling convention may not be as expected. "
                                         "A future version of Halide will make this illegal, and require all Inputs to be declared before all Outputs. "
                                         "(You can avoid this requirement by overriding Generator::allow_out_of_order_inputs_and_outputs().)";

    bool outputs_seen = false;
    auto vf = ObjectInstanceRegistry::instances_in_range(generator, size);
    for (const auto &vi : vf) {
        void *const instance = vi.first;
        const ObjectInstanceRegistry::Kind kind = vi.second;
        switch (kind) {
        case ObjectInstanceRegistry::GeneratorParam: {
            auto *param = static_cast<GeneratorParamBase *>(instance);
            internal_assert(param != nullptr);
            user_assert(is_valid_name(param->name())) << "Invalid GeneratorParam name: " << param->name();
            user_assert(!names.count(param->name())) << "Duplicate GeneratorParam name: " << param->name();
            names.insert(param->name());
            internal_assert(param->generator == nullptr || param->generator == generator);
            param->generator = generator;
            filter_generator_params.push_back(param);
            break;
        }
        case ObjectInstanceRegistry::GeneratorInput: {
            if (outputs_seen) {
                if (!generator->allow_out_of_order_inputs_and_outputs()) {
                    user_warning << io_order_warning;
                }
            }
            auto *input = static_cast<Internal::GeneratorInputBase *>(instance);
            internal_assert(input != nullptr);
            user_assert(is_valid_name(input->name())) << "Invalid Input name: (" << input->name() << ")\n";
            user_assert(!names.count(input->name())) << "Duplicate Input name: " << input->name();
            names.insert(input->name());
            internal_assert(input->generator == nullptr || input->generator == generator);
            input->generator = generator;
            filter_inputs.push_back(input);
            add_synthetic_params(input);
            break;
        }
        case ObjectInstanceRegistry::GeneratorOutput: {
            outputs_seen = true;
            auto *output = static_cast<Internal::GeneratorOutputBase *>(instance);
            internal_assert(output != nullptr);
            user_assert(is_valid_name(output->name())) << "Invalid Output name: (" << output->name() << ")\n";
            user_assert(!names.count(output->name())) << "Duplicate Output name: " << output->name();
            names.insert(output->name());
            internal_assert(output->generator == nullptr || output->generator == generator);
            output->generator = generator;
            filter_outputs.push_back(output);
            add_synthetic_params(output);
            break;
        }
        case ObjectInstanceRegistry::Generator:
            // nothing
            break;
        case ObjectInstanceRegistry::FilterParam:
            user_error << "ImageParam and Param<> are no longer allowed in Generators; use Input<> instead.";
            break;
        default:
            user_error << "Unexpected ObjectInstanceRegistry::Kind value in GeneratorParamInfo. " << (int)kind;
            break;
        }
    }

    for (auto &g : owned_synthetic_params) {
        g->generator = generator;
    }
}

GeneratorParamInfo &GeneratorBase::param_info() {
    internal_assert(param_info_ptr != nullptr);
    return *param_info_ptr;
}

GeneratorInputBase *GeneratorBase::find_input_by_name(const std::string &name) {
    auto *t = GeneratorBase::find_by_name(name, param_info().inputs());
    internal_assert(t != nullptr) << "Input " << name << " not found.";
    return t;
}

GeneratorOutputBase *GeneratorBase::find_output_by_name(const std::string &name) {
    auto *t = GeneratorBase::find_by_name(name, param_info().outputs());
    internal_assert(t != nullptr) << "Output " << name << " not found.";
    return t;
}

GeneratorContext GeneratorBase::context() const {
    return GeneratorContext(target, autoscheduler_.value());
}

void GeneratorBase::init_from_context(const Halide::GeneratorContext &context) {
    target.set(context.target_);
    autoscheduler_.set(context.autoscheduler_params_);

    // preemptively build our param_info now
    internal_assert(param_info_ptr == nullptr);
    param_info_ptr = std::make_unique<GeneratorParamInfo>(this, size);
}

void GeneratorBase::set_generator_names(const std::string &registered_name, const std::string &stub_name) {
    user_assert(is_valid_name(registered_name)) << "Invalid Generator name: " << registered_name;
    internal_assert(!registered_name.empty() && !stub_name.empty());
    internal_assert(generator_registered_name.empty() && generator_stub_name.empty());
    generator_registered_name = registered_name;
    generator_stub_name = stub_name;
}

void GeneratorBase::set_inputs_vector(const std::vector<std::vector<StubInput>> &inputs) {
    ensure_configure_has_been_called();
    advance_phase(InputsSet);
    GeneratorParamInfo &pi = param_info();
    user_assert(inputs.size() == pi.inputs().size())
        << "Expected exactly " << pi.inputs().size()
        << " inputs but got " << inputs.size() << "\n";
    for (size_t i = 0; i < pi.inputs().size(); ++i) {
        pi.inputs()[i]->set_inputs(inputs[i]);
    }
}

void GeneratorBase::check_min_phase(Phase expected_phase) const {
    user_assert(phase >= expected_phase) << "You may not do this operation at this phase.";
}

void GeneratorBase::check_exact_phase(Phase expected_phase) const {
    user_assert(phase == expected_phase) << "You may not do this operation at this phase.";
}

void GeneratorBase::advance_phase(Phase new_phase) {
    switch (new_phase) {
    case Created:
        internal_error << "Impossible";
        break;
    case ConfigureCalled:
        internal_assert(phase == Created);
        break;
    case InputsSet:
        internal_assert(phase == Created || phase == ConfigureCalled || phase == InputsSet);
        break;
    case GenerateCalled:
        // It's OK to advance directly to GenerateCalled.
        internal_assert(phase == Created || phase == ConfigureCalled || phase == InputsSet);
        break;
    case ScheduleCalled:
        internal_assert(phase == GenerateCalled);
        break;
    }
    phase = new_phase;
}

void GeneratorBase::ensure_configure_has_been_called() {
    if (phase < ConfigureCalled) {
        call_configure();
    }
    check_min_phase(ConfigureCalled);
}

void GeneratorBase::pre_configure() {
    advance_phase(ConfigureCalled);
}

void GeneratorBase::post_configure() {
}

void GeneratorBase::pre_generate() {
    advance_phase(GenerateCalled);
    GeneratorParamInfo &pi = param_info();
    user_assert(!pi.outputs().empty()) << "Must use Output<> with generate() method.";
    user_assert(get_target() != Target()) << "The Generator target has not been set.";

    for (auto *input : pi.inputs()) {
        input->init_internals();
    }
    for (auto *output : pi.outputs()) {
        output->init_internals();
    }
}

void GeneratorBase::post_generate() {
}

void GeneratorBase::pre_schedule() {
    advance_phase(ScheduleCalled);
}

void GeneratorBase::post_schedule() {
}

void GeneratorBase::add_requirement(const Expr &condition, const std::vector<Expr> &error_args) {
    internal_assert(!pipeline.defined());
    requirements.push_back({condition, error_args});
}

Pipeline GeneratorBase::get_pipeline() {
    check_min_phase(GenerateCalled);
    if (!pipeline.defined()) {
        GeneratorParamInfo &pi = param_info();
        user_assert(!pi.outputs().empty()) << "Must use get_pipeline<> with Output<>.";
        std::vector<Func> funcs;
        for (auto *output : pi.outputs()) {
            for (const auto &f : output->funcs()) {
                user_assert(f.defined()) << "Output \"" << f.name() << "\" was not defined.\n";
                if (output->dims_defined()) {
                    user_assert(f.dimensions() == output->dims()) << "Output \"" << f.name()
                                                                  << "\" requires dimensions=" << output->dims()
                                                                  << " but was defined as dimensions=" << f.dimensions() << ".\n";
                }
                if (output->gio_types_defined()) {
                    user_assert((int)f.outputs() == (int)output->gio_types().size()) << "Output \"" << f.name()
                                                                                     << "\" requires a Tuple of size " << output->gio_types().size()
                                                                                     << " but was defined as Tuple of size " << f.outputs() << ".\n";
                    for (size_t i = 0; i < f.types().size(); ++i) {
                        Type expected = output->gio_types().at(i);
                        Type actual = f.types()[i];
                        user_assert(expected == actual) << "Output \"" << f.name()
                                                        << "\" requires type " << expected
                                                        << " but was defined as type " << actual << ".\n";
                    }
                }
                funcs.push_back(f);
            }
        }
        pipeline = Pipeline(funcs);
        for (const auto &r : requirements) {
            pipeline.add_requirement(r.condition, r.error_args);
        }
    }
    return pipeline;
}

void GeneratorBase::check_scheduled(const char *m) const {
    check_min_phase(ScheduleCalled);
}

void GeneratorBase::check_input_is_singular(Internal::GeneratorInputBase *in) {
    user_assert(!in->is_array())
        << "Input " << in->name() << " is an array, and must be set with a vector type.";
}

void GeneratorBase::check_input_is_array(Internal::GeneratorInputBase *in) {
    user_assert(in->is_array())
        << "Input " << in->name() << " is not an array, and must not be set with a vector type.";
}

void GeneratorBase::check_input_kind(Internal::GeneratorInputBase *in, Internal::ArgInfoKind kind) {
    user_assert(in->kind() == kind)
        << "Input " << in->name() << " cannot be set with the type specified.";
}

void GeneratorBase::set_generatorparam_value(const std::string &name, const std::string &value) {
    user_assert(name != "target") << "The GeneratorParam named " << name << " cannot be set by set_generatorparam_value().\n";
    if (autoscheduler_.try_set(name, value)) {
        return;
    }

    GeneratorParamInfo &pi = param_info();

    for (auto *g : pi.generator_params()) {
        if (g->name() != name) {
            continue;
        }
        g->set_from_string(value);
        return;
    }
    user_error
        << "Generator " << generator_registered_name << " has no GeneratorParam named: " << name << "\n";
}

void GeneratorBase::set_generatorparam_value(const std::string &name, const LoopLevel &value) {
    GeneratorParamInfo &pi = param_info();
    for (auto *g : pi.generator_params()) {
        if (g->name() != name) {
            continue;
        }
        user_assert(g->is_looplevel_param()) << "GeneratorParam " << name << " is not a LoopLevel and cannot be set this way.";
        g->set(value);
        return;
    }
    user_error
        << "Generator " << generator_registered_name << " has no GeneratorParam named: " << name << "\n";
}

std::string GeneratorBase::name() {
    return generator_registered_name;
}

std::vector<AbstractGenerator::ArgInfo> GeneratorBase::arginfos() {
    ensure_configure_has_been_called();
    std::vector<AbstractGenerator::ArgInfo> args;
    args.reserve(param_info().inputs().size() + param_info().outputs().size());
    GeneratorBase::get_arguments(args, ArgInfoDirection::Input, param_info().inputs());
    GeneratorBase::get_arguments(args, ArgInfoDirection::Output, param_info().outputs());
    return args;
}

bool GeneratorBase::allow_out_of_order_inputs_and_outputs() const {
    return false;
}

std::vector<Parameter> GeneratorBase::input_parameter(const std::string &name) {
    auto *input = find_input_by_name(name);

    const size_t params_size = input->parameters_.size();
    const bool is_buffer = input->kind() != ArgInfoKind::Scalar;
    if (is_buffer) {
        internal_assert(input->exprs_.empty() && input->funcs_.size() == params_size);
    } else {
        internal_assert(input->funcs_.empty() && input->exprs_.size() == params_size);
    }

    std::vector<Parameter> params;
    params.reserve(params_size);

    for (size_t i = 0; i < params_size; ++i) {
        const auto &p = input->parameters_[i];
        internal_assert(p.is_buffer() == is_buffer);
        const auto name = input->array_name(i);
        internal_assert(p.name() == name) << "input name was " << p.name() << " expected " << name;
        const int expected_dimensions = is_buffer ? input->funcs_[i].dimensions() : 0;
        internal_assert(p.dimensions() == expected_dimensions) << "input dimensions was " << p.dimensions() << " expected " << expected_dimensions;
        internal_assert(p.type() == input->gio_type()) << "input type was " << p.type() << " expected " << input->gio_type();
        params.push_back(p);
    }
    return params;
}

std::vector<Func> GeneratorBase::output_func(const std::string &n) {
    check_min_phase(GenerateCalled);
    auto *output = find_output_by_name(n);
    // Call for the side-effect of asserting if the value isn't defined.
    (void)output->array_size();
    for (const auto &f : output->funcs()) {
        user_assert(f.defined()) << "Output " << n << " was not fully defined.\n";
    }
    return output->funcs();
}

void GeneratorBase::bind_input(const std::string &name, const std::vector<Parameter> &v) {
    ensure_configure_has_been_called();
    advance_phase(InputsSet);
    std::vector<StubInput> si;
    std::copy(v.begin(), v.end(), std::back_inserter(si));
    find_input_by_name(name)->set_inputs(si);
}

void GeneratorBase::bind_input(const std::string &name, const std::vector<Func> &v) {
    ensure_configure_has_been_called();
    advance_phase(InputsSet);
    std::vector<StubInput> si;
    std::copy(v.begin(), v.end(), std::back_inserter(si));
    find_input_by_name(name)->set_inputs(si);
}

void GeneratorBase::bind_input(const std::string &name, const std::vector<Expr> &v) {
    ensure_configure_has_been_called();
    advance_phase(InputsSet);
    std::vector<StubInput> si;
    std::copy(v.begin(), v.end(), std::back_inserter(si));
    find_input_by_name(name)->set_inputs(si);
}

bool GeneratorBase::emit_cpp_stub(const std::string &stub_file_path) {
    user_assert(!generator_registered_name.empty() && !generator_stub_name.empty()) << "Generator has no name.\n";
    // Make sure we call configure() so that extra inputs/outputs are added as necessary.
    ensure_configure_has_been_called();
    // StubEmitter will want to access the GP/SP values, so advance the phase to avoid assert-fails.
    advance_phase(GenerateCalled);
    advance_phase(ScheduleCalled);
    GeneratorParamInfo &pi = param_info();
    std::ofstream file(stub_file_path);
    StubEmitter emit(file, generator_registered_name, generator_stub_name, pi.generator_params(), pi.inputs(), pi.outputs());
    emit.emit();
    return true;
}

bool GeneratorBase::emit_hlpipe(const std::string &hlpipe_file_path) {
#ifdef WITH_SERIALIZATION
    user_assert(!generator_registered_name.empty() && !generator_stub_name.empty()) << "Generator has no name.\n";
    Pipeline pipeline = build_pipeline();
    AutoSchedulerResults auto_schedule_results;
    const auto context = this->context();
    const auto &asp = context.autoscheduler_params();
    if (!asp.name.empty()) {
        debug(1) << "Applying autoscheduler " << asp.name << " to Generator " << name() << " ...\n";
        auto_schedule_results = pipeline.apply_autoscheduler(context.target(), asp);
    }
    std::map<std::string, Parameter> params;  // FIXME: Remove when API allows this to be optional
    serialize_pipeline(pipeline, hlpipe_file_path, params);
    return true;
#else
    user_error << "Serialization is not supported in this build of Halide; try rebuilding with WITH_SERIALIZATION=ON.";
    return false;
#endif
}

GIOBase::GIOBase(size_t array_size,
                 const std::string &name,
                 ArgInfoKind kind,
                 const std::vector<Type> &types,
                 int dims)
    : array_size_(array_size), name_(name), kind_(kind), types_(types), dims_(dims) {
}

bool GIOBase::array_size_defined() const {
    return array_size_ != -1;
}

size_t GIOBase::array_size() const {
    user_assert(array_size_defined()) << "ArraySize is unspecified for " << input_or_output() << "'" << name() << "'; you need to explicitly set it via the resize() method or by setting '"
                                      << name() << ".size' in your build rules.";
    return (size_t)array_size_;
}

bool GIOBase::is_array() const {
    internal_error << "Unimplemented";
    return false;
}

const std::string &GIOBase::name() const {
    return name_;
}

ArgInfoKind GIOBase::kind() const {
    return kind_;
}

bool GIOBase::gio_types_defined() const {
    return !types_.empty();
}

const std::vector<Type> &GIOBase::gio_types() const {
    // If types aren't defined, but we have one Func that is,
    // we probably just set an Output<Func> and should propagate the types.
    if (!gio_types_defined()) {
        // use funcs_, not funcs(): the latter could give a much-less-helpful error message
        // in this case.
        const auto &f = funcs_;
        if (f.size() == 1 && f.at(0).defined()) {
            check_matching_types(f.at(0).types());
        }
    }
    user_assert(gio_types_defined()) << "Type is not defined for " << input_or_output() << " '" << name() << "'; you may need to specify '" << name() << ".type' as a GeneratorParam, or call set_type() from the configure() method.\n";
    return types_;
}

Type GIOBase::gio_type() const {
    const auto &t = gio_types();
    internal_assert(t.size() == 1) << "Expected types_.size() == 1, saw " << t.size() << " for " << name() << "\n";
    return t.at(0);
}

void GIOBase::set_type(const Type &type) {
    generator->check_exact_phase(GeneratorBase::ConfigureCalled);
    user_assert(!gio_types_defined()) << "set_type() may only be called on an Input or Output that has no type specified.";
    types_ = {type};
}

// Conceptually related to the method above, but attached to the
// GeneratorOutputBase subclass instead of GIOBase because currently input
// buffers can't be tuples.
void GeneratorOutputBase::set_type(const std::vector<Type> &types) {
    generator->check_exact_phase(GeneratorBase::ConfigureCalled);
    user_assert(!gio_types_defined()) << "set_type() may only be called on an Input or Output that has no type specified.";
    types_ = types;
}

void GIOBase::set_dimensions(int dims) {
    generator->check_exact_phase(GeneratorBase::ConfigureCalled);
    user_assert(!dims_defined()) << "set_dimensions() may only be called on an Input or Output that has no dimensionality specified.";
    dims_ = dims;
}

void GIOBase::set_array_size(int size) {
    generator->check_exact_phase(GeneratorBase::ConfigureCalled);
    user_assert(!array_size_defined()) << "set_array_size() may only be called on an Input or Output that has no array size specified.";
    array_size_ = size;
}

bool GIOBase::dims_defined() const {
    return dims_ != -1;
}

int GIOBase::dims() const {
    // If types aren't defined, but we have one Func that is,
    // we probably just set an Output<Func> and should propagate the types.
    if (!dims_defined()) {
        // use funcs_, not funcs(): the latter could give a much-less-helpful error message
        // in this case.
        const auto &f = funcs_;
        if (f.size() == 1 && f.at(0).defined()) {
            check_matching_dims(funcs().at(0).dimensions());
        }
    }
    user_assert(dims_defined()) << "Dimensions are not defined for " << input_or_output() << " '" << name() << "'; you may need to specify '" << name() << ".dim' as a GeneratorParam.\n";
    return dims_;
}

const std::vector<Func> &GIOBase::funcs() const {
    internal_assert(funcs_.size() == array_size() && exprs_.empty());
    return funcs_;
}

const std::vector<Expr> &GIOBase::exprs() const {
    internal_assert(exprs_.size() == array_size() && funcs_.empty());
    return exprs_;
}

void GIOBase::verify_internals() {
    user_assert(dims_ >= 0) << "Generator Input/Output Dimensions must have positive values";

    if (kind() != ArgInfoKind::Scalar) {
        for (const Func &f : funcs()) {
            user_assert(f.defined()) << "Input/Output " << name() << " is not defined.\n";
            user_assert(f.dimensions() == dims())
                << "Expected dimensions " << dims()
                << " but got " << f.dimensions()
                << " for " << name() << "\n";
            user_assert(f.outputs() == 1)
                << "Expected outputs() == " << 1
                << " but got " << f.outputs()
                << " for " << name() << "\n";
            user_assert(f.types().size() == 1)
                << "Expected types().size() == " << 1
                << " but got " << f.outputs()
                << " for " << name() << "\n";
            user_assert(f.types()[0] == gio_type())
                << "Expected type " << gio_type()
                << " but got " << f.types()[0]
                << " for " << name() << "\n";
        }
    } else {
        for (const Expr &e : exprs()) {
            user_assert(e.defined()) << "Input/Output " << name() << " is not defined.\n";
            user_assert(e.type() == gio_type())
                << "Expected type " << gio_type()
                << " but got " << e.type()
                << " for " << name() << "\n";
        }
    }
}

std::string GIOBase::array_name(size_t i) const {
    std::string n = name();
    if (is_array()) {
        n += "_" + std::to_string(i);
    }
    return n;
}

// If our type(s) are defined, ensure it matches the ones passed in, asserting if not.
// If our type(s) are not defined, just set to the ones passed in.
void GIOBase::check_matching_types(const std::vector<Type> &t) const {
    if (gio_types_defined()) {
        user_assert(gio_types().size() == t.size()) << "Type mismatch for " << name() << ": expected " << gio_types().size() << " types but saw " << t.size();
        for (size_t i = 0; i < t.size(); ++i) {
            user_assert(gio_types().at(i) == t.at(i)) << "Type mismatch for " << name() << ": expected " << gio_types().at(i) << " saw " << t.at(i);
        }
    } else {
        types_ = t;
    }
}

void GIOBase::check_gio_access() const {
    // // Allow reading when no Generator is set, to avoid having to special-case ctor initing code
    if (!generator) {
        return;
    }
    user_assert(generator->phase > GeneratorBase::InputsSet)
        << "The " << input_or_output() << " \"" << name() << "\" cannot be examined before generate() is called.\n";
}

// If our dims are defined, ensure it matches the one passed in, asserting if not.
// If our dims are not defined, just set to the one passed in.
void GIOBase::check_matching_dims(int d) const {
    internal_assert(d >= 0);
    if (dims_defined()) {
        user_assert(dims() == d) << "Dimensions mismatch for " << name() << ": expected " << dims() << " saw " << d;
    } else {
        dims_ = d;
    }
}

void GIOBase::check_matching_array_size(size_t size) const {
    if (array_size_defined()) {
        user_assert(array_size() == size) << "ArraySize mismatch for " << name() << ": expected " << array_size() << " saw " << size;
    } else {
        array_size_ = size;
    }
}

GeneratorInputBase::GeneratorInputBase(size_t array_size,
                                       const std::string &name,
                                       ArgInfoKind kind,
                                       const std::vector<Type> &t,
                                       int d)
    : GIOBase(array_size, name, kind, t, d) {
    ObjectInstanceRegistry::register_instance(this, 0, ObjectInstanceRegistry::GeneratorInput, this);
}

GeneratorInputBase::GeneratorInputBase(const std::string &name, ArgInfoKind kind, const std::vector<Type> &t, int d)
    : GeneratorInputBase(1, name, kind, t, d) {
    // nothing
}

GeneratorInputBase::~GeneratorInputBase() {
    ObjectInstanceRegistry::unregister_instance(this);
}

void GeneratorInputBase::check_value_writable() const {
    user_assert(generator && generator->phase == GeneratorBase::InputsSet)
        << "The Input " << name() << " cannot be set at this point.\n";
}

void GeneratorInputBase::set_def_min_max() {
    // nothing
}

Parameter GeneratorInputBase::parameter() const {
    user_assert(!this->is_array()) << "Cannot call the parameter() method on Input<[]> " << name() << "; use an explicit subscript operator instead.";
    return parameters_.at(0);
}

void GeneratorInputBase::verify_internals() {
    GIOBase::verify_internals();

    const size_t expected = (kind() != ArgInfoKind::Scalar) ? funcs().size() : exprs().size();
    user_assert(parameters_.size() == expected) << "Expected parameters_.size() == "
                                                << expected << ", saw " << parameters_.size() << " for " << name() << "\n";
}

void GeneratorInputBase::init_internals() {
    if (inputs_set) {
        return;
    }

    // Call these for the side-effect of asserting if the values aren't defined.
    (void)array_size();
    (void)gio_types();
    (void)dims();

    parameters_.clear();
    exprs_.clear();
    funcs_.clear();
    for (size_t i = 0; i < array_size(); ++i) {
        auto name = array_name(i);
        parameters_.emplace_back(gio_type(), kind() != ArgInfoKind::Scalar, dims(), name);
        auto &p = parameters_[i];
        if (kind() != ArgInfoKind::Scalar) {
            internal_assert(dims() == p.dimensions());
            funcs_.push_back(make_param_func(p, name));
        } else {
            Expr e = Internal::Variable::make(gio_type(), name, p);
            exprs_.push_back(e);
        }
    }

    set_def_min_max();
    verify_internals();
}

void GeneratorInputBase::set_inputs(const std::vector<StubInput> &inputs) {
    generator->check_exact_phase(GeneratorBase::InputsSet);
    parameters_.clear();
    exprs_.clear();
    funcs_.clear();
    check_matching_array_size(inputs.size());
    for (size_t i = 0; i < inputs.size(); ++i) {
        const StubInput &in = inputs.at(i);
        user_assert(in.kind() == kind()) << "An input for " << name() << " is not of the expected kind.\n";
        if (kind() == ArgInfoKind::Function) {
            auto f = in.func();
            user_assert(f.defined()) << "The input for " << name() << " is an undefined Func. Please define it.\n";
            check_matching_types(f.types());
            check_matching_dims(f.dimensions());
            funcs_.push_back(f);
            parameters_.emplace_back(f.types().at(0), true, f.dimensions(), array_name(i));
        } else if (kind() == ArgInfoKind::Buffer) {
            auto p = in.parameter();
            user_assert(p.defined()) << "The input for " << name() << " is an undefined Buffer. Please define it.\n";
            check_matching_types({p.type()});
            check_matching_dims(p.dimensions());
            funcs_.push_back(make_param_func(p, name()));
            parameters_.push_back(p);
        } else {
            auto e = in.expr();
            user_assert(e.defined()) << "The input for " << name() << " is an undefined Expr. Please define it.\n";
            check_matching_types({e.type()});
            check_matching_dims(0);
            exprs_.push_back(e);
            parameters_.emplace_back(e.type(), false, 0, array_name(i));
        }
    }

    set_def_min_max();
    verify_internals();
    inputs_set = true;
}

void GeneratorInputBase::set_estimate_impl(const Var &var, const Expr &min, const Expr &extent) {
    internal_assert(exprs_.empty() && !funcs_.empty() && parameters_.size() == funcs_.size());
    for (size_t i = 0; i < funcs_.size(); ++i) {
        Func &f = funcs_[i];
        f.set_estimate(var, min, extent);
        // Propagate the estimate into the Parameter as well, just in case
        // we end up compiling this for toplevel.
        std::vector<Var> args = f.args();
        int dim = -1;
        for (size_t a = 0; a < args.size(); ++a) {
            if (args[a].same_as(var)) {
                dim = a;
                break;
            }
        }
        internal_assert(dim >= 0);
        Parameter &p = parameters_[i];
        p.set_min_constraint_estimate(dim, min);
        p.set_extent_constraint_estimate(dim, extent);
    }
}

void GeneratorInputBase::set_estimates_impl(const Region &estimates) {
    internal_assert(exprs_.empty() && !funcs_.empty() && parameters_.size() == funcs_.size());
    for (size_t i = 0; i < funcs_.size(); ++i) {
        Func &f = funcs_[i];
        f.set_estimates(estimates);
        // Propagate the estimate into the Parameter as well, just in case
        // we end up compiling this for toplevel.
        for (size_t dim = 0; dim < estimates.size(); ++dim) {
            Parameter &p = parameters_[i];
            const Range &r = estimates[dim];
            p.set_min_constraint_estimate(dim, r.min);
            p.set_extent_constraint_estimate(dim, r.extent);
        }
    }
}

GeneratorOutputBase::GeneratorOutputBase(size_t array_size, const std::string &name, ArgInfoKind kind, const std::vector<Type> &t, int d)
    : GIOBase(array_size, name, kind, t, d) {
    internal_assert(kind != ArgInfoKind::Scalar);
    ObjectInstanceRegistry::register_instance(this, 0, ObjectInstanceRegistry::GeneratorOutput, this);
}

GeneratorOutputBase::GeneratorOutputBase(const std::string &name, ArgInfoKind kind, const std::vector<Type> &t, int d)
    : GeneratorOutputBase(1, name, kind, t, d) {
    // nothing
}

GeneratorOutputBase::~GeneratorOutputBase() {
    ObjectInstanceRegistry::unregister_instance(this);
}

void GeneratorOutputBase::check_value_writable() const {
    user_assert(generator && generator->phase == GeneratorBase::GenerateCalled)
        << "The Output " << name() << " can only be set inside generate().\n";
}

void GeneratorOutputBase::init_internals() {
    exprs_.clear();
    funcs_.clear();
    if (array_size_defined()) {
        const auto t = gio_types_defined() ? gio_types() : std::vector<Type>{};
        const int d = dims_defined() ? dims() : -1;
        for (size_t i = 0; i < array_size(); ++i) {
            funcs_.emplace_back(t, d, array_name(i));
        }
    }
}

void GeneratorOutputBase::resize(size_t size) {
    internal_assert(is_array());
    internal_assert(!array_size_defined()) << "You may only call " << name()
                                           << ".resize() when then size is undefined\n";
    array_size_ = (int)size;
    init_internals();
}

StubOutputBufferBase::StubOutputBufferBase() = default;

StubOutputBufferBase::StubOutputBufferBase(const Func &f, const std::shared_ptr<AbstractGenerator> &generator)
    : f(f), generator(generator) {
}

Realization StubOutputBufferBase::realize(std::vector<int32_t> sizes) {
    return f.realize(std::move(sizes), get_target());
}

Target StubOutputBufferBase::get_target() const {
    return generator->context().target();
}

RegisterGenerator::RegisterGenerator(const char *registered_name, GeneratorFactory generator_factory) {
    Internal::GeneratorRegistry::register_factory(registered_name, std::move(generator_factory));
}

void generator_test() {
    GeneratorContext context(get_host_target().without_feature(Target::Profile));

    // Verify that the Generator's internal phase actually prevents unsupported
    // order of operations.
    {
        class Tester : public Generator<Tester> {
        public:
            GeneratorParam<int> gp0{"gp0", 0};
            GeneratorParam<float> gp1{"gp1", 1.f};
            GeneratorParam<uint64_t> gp2{"gp2", 2};

            Input<int> input{"input"};
            Output<Func> output{"output", Int(32), 1};

            void generate() {
                internal_assert(gp0 == 1);
                internal_assert(gp1 == 2.f);
                internal_assert(gp2 == (uint64_t)2);  // unchanged
                Var x;
                output(x) = input + gp0;
            }
            void schedule() {
                // empty
            }
        };

        Tester tester;
        tester.init_from_context(context);
        internal_assert(tester.phase == GeneratorBase::Created);

        // Verify that calling GeneratorParam::set() works.
        tester.gp0.set(1);

        tester.set_inputs_vector({{StubInput(42)}});
        internal_assert(tester.phase == GeneratorBase::InputsSet);

        // tester.set_inputs_vector({{StubInput(43)}});  // This will assert-fail.

        // Also ok to call in this phase.
        tester.gp1.set(2.f);

        tester.call_generate();
        internal_assert(tester.phase == GeneratorBase::GenerateCalled);

        // tester.set_inputs_vector({{StubInput(44)}});  // This will assert-fail.
        // tester.gp2.set(2);  // This will assert-fail.

        tester.call_schedule();
        internal_assert(tester.phase == GeneratorBase::ScheduleCalled);

        // tester.set_inputs_vector({{StubInput(45)}});  // This will assert-fail.
        // tester.gp2.set(2);  // This will assert-fail.
        // tester.sp2.set(202);  // This will assert-fail.
    }

    // Verify that set_inputs() works properly, even if the specific subtype of Generator is not known.
    {
        class Tester : public Generator<Tester> {
        public:
            Input<int> input_int{"input_int"};
            Input<float> input_float{"input_float"};
            Input<uint8_t> input_byte{"input_byte"};
            Input<uint64_t[4]> input_scalar_array{"input_scalar_array"};
            Input<Func> input_func_typed{"input_func_typed", Int(16), 1};
            Input<Func> input_func_untyped{"input_func_untyped", 1};
            Input<Func[]> input_func_array{"input_func_array", 1};
            Input<Buffer<uint8_t, 3>> input_buffer_typed{"input_buffer_typed"};
            Input<Buffer<>> input_buffer_untyped{"input_buffer_untyped"};
            Output<Func> output{"output", Float(32), 1};

            void generate() {
                Var x;
                output(x) = input_int +
                            input_float +
                            input_byte +
                            input_scalar_array[3] +
                            input_func_untyped(x) +
                            input_func_typed(x) +
                            input_func_array[0](x) +
                            input_buffer_typed(x, 0, 0) +
                            input_buffer_untyped(x, Halide::_);
            }
            void schedule() {
                // nothing
            }
        };

        Tester tester_instance;
        tester_instance.init_from_context(context);
        // Use a base-typed reference to verify the code below doesn't know about subtype
        GeneratorBase &tester = tester_instance;

        const int i = 1234;
        const float f = 2.25f;
        const uint8_t b = 0x42;
        const std::vector<uint64_t> a = {1, 2, 3, 4};
        Var x;
        Func fn_typed, fn_untyped;
        fn_typed(x) = make_const(Int(16), 38);
        fn_untyped(x) = 32.f;
        const std::vector<Func> fn_array = {fn_untyped, fn_untyped};

        Buffer<uint8_t> buf_typed(1, 1, 1);
        Buffer<float> buf_untyped(1);

        buf_typed.fill(33);
        buf_untyped.fill(34);

        // set_inputs() requires inputs in Input<>-decl-order,
        // and all inputs match type exactly.
        tester.set_inputs(i, f, b, a, fn_typed, fn_untyped, fn_array, buf_typed, buf_untyped);
        tester.call_generate();
        tester.call_schedule();

        Buffer<float> im = tester_instance.realize({1});
        internal_assert(im.dimensions() == 1);
        internal_assert(im.dim(0).extent() == 1);
        internal_assert(im(0) == 1475.25f) << "Expected 1475.25 but saw " << im(0);
    }

    // Verify that array inputs and outputs are typed correctly.
    {
        class Tester : public Generator<Tester> {
        public:
            Input<int[]> expr_array_input{"expr_array_input"};
            Input<Func[]> func_array_input{"input_func_array"};
            Input<Buffer<>[]> buffer_array_input{"buffer_array_input"};

            Input<int[]> expr_array_output{"expr_array_output"};
            Output<Func[]> func_array_output{"func_array_output"};
            Output<Buffer<>[]> buffer_array_output{"buffer_array_output"};

            void generate() {
            }
        };

        Tester tester_instance;

        static_assert(std::is_same_v<decltype(tester_instance.expr_array_input[0]), const Expr &>, "type mismatch");
        static_assert(std::is_same_v<decltype(tester_instance.expr_array_output[0]), const Expr &>, "type mismatch");

        static_assert(std::is_same_v<decltype(tester_instance.func_array_input[0]), const Func &>, "type mismatch");
        static_assert(std::is_same_v<decltype(tester_instance.func_array_output[0]), Func &>, "type mismatch");

        static_assert(std::is_same_v<decltype(tester_instance.buffer_array_input[0]), ImageParam>, "type mismatch");
        static_assert(std::is_same_v<decltype(tester_instance.buffer_array_output[0]), Func>, "type mismatch");
    }

    class GPTester : public Generator<GPTester> {
    public:
        GeneratorParam<int> gp{"gp", 0};
        Output<Func> output{"output", Int(32), 0};

        void generate() {
            internal_assert(get_target().has_feature(Target::Profile));
            output() = 0;
        }
        void schedule() {
        }

        // Test that we can override init_from_context() to modify the target
        // we use. (Generally speaking, your code probably should ever need to
        // do this; this code only does it for testing purposes. See comments
        // in Generator.h.)
        void init_from_context(const GeneratorContext &context) override {
            auto t = context.target().with_feature(Target::Profile);
            Generator<GPTester>::init_from_context(context.with_target(t));
        }
    };
    GPTester gp_tester;
    gp_tester.init_from_context(context);
    // Accessing the GeneratorParam will assert-fail if we
    // don't do some minimal setup here.
    gp_tester.set_inputs_vector({});
    gp_tester.call_generate();
    gp_tester.call_schedule();
    auto &gp = gp_tester.gp;

    // Verify that RDom parameter-pack variants can convert GeneratorParam to Expr
    RDom rdom(0, gp, 0, gp);

    // Verify that Func parameter-pack variants can convert GeneratorParam to Expr
    Var x, y;
    Func f, g;
    f(x, y) = x + y;
    g(x, y) = f(gp, gp);  // check Func::operator() overloads
    g(rdom.x, rdom.y) += f(rdom.x, rdom.y);
    g.update(0).reorder(rdom.y, rdom.x);  // check Func::reorder() overloads for RDom::operator RVar()

    // Verify that print() parameter-pack variants can convert GeneratorParam to Expr
    print(f(0, 0), g(1, 1), gp);
    print_when(true, f(0, 0), g(1, 1), gp);

    // Verify that Tuple parameter-pack variants can convert GeneratorParam to Expr
    Tuple t(gp, gp, gp);

    std::cout << "Generator test passed\n";
}

}  // namespace Internal
}  // namespace Halide